Idealy, we want hikashop to be compatible with all the payment systems out there. However, we won't be able to do all of them by ourselves and at the same time add all the other features people are already requesting. So it's in the todo list but more at the bottom than at the top.
Also note that HikaShop provides an interface to write payment plugins. Anyone who knows PHP could make one by looking at our integration documentation and all the other payment plugins we already did:
www.hikashop.com/en/support/documentation/62.html

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